The Official Gazette of Japanese Patent No. 3290047 discloses in FIG. 1 on page 6 a semiconductor acceleration sensor wherein part of a weight is disposed in an internal space of an acceleration sensor body. In this semiconductor acceleration sensor, an inner peripheral surface of a support surrounding the internal space and an outer peripheral surface of the weight are respectively formed as an inclined surface so as to be parallel with each other, which consequently increases the mass of the weight.
In such a semiconductor acceleration sensor of the above-mentioned construction, however, such consideration is not given that a diaphragm portion of a semiconductor sensor element is prevented from being damaged by restraining the movement of the weight when acceleration toward the semiconductor sensor element is added to the mass-increased weight (in a vertical axis direction). Consequently, if large acceleration is added to the mass-increased weight, the semiconductor sensor element is damaged. In addition, such a conventional semiconductor acceleration sensor requires a complicated manufacturing process for making the inner peripheral surface of the semiconductor sensor element and the outer peripheral surface of the weight accurately parallel to each other, and for aligning a center of the weight with that of the semiconductor sensor element.
Accordingly, an object of the present invention is to provide a semiconductor acceleration sensor wherein a semiconductor sensor element is not damaged even when disposing at least part of a weight in an internal space of the semiconductor sensor element and increasing the mass of a weight.
Another object of the present invention is to provide a semiconductor acceleration sensor which does not require a complicated manufacturing process for aligning the weight relative to a support of the acceleration sensor body.
Still another object of the present invention is to provide a semiconductor acceleration sensor which is capable of reducing discrepancy of the central position between the weight and the support portion when the weight is displaced in a direction where a diaphragm portion is located and lessening variations in performance in spite of dimensional errors in manufacturing the support portion and weight.
Yet another object of the present invention is to provide a semiconductor acceleration sensor which is capable of readily and accurately aligning the center of the weight with that of the acceleration sensor body, and a manufacturing method thereof.